The ignition switch and starter needed to be replaced around 36,000mi.
The right front caliper froze & was replaced at 39,000mi.
The electric choke stopped working at 42,000mi.
The (ancient) springs and shocks had to be replaced at 44,000mi.
The A/C compressor seized around 45,000mi.
Rear main seal started leaking at about 47,000mi.
All 4 ball joints, & the upper control arm bushings, were worn out by 48,000mi.
The left backup light repeatedly burned out (probably a short)
The original AM/FM radio was temperamental - apparently it needed to warm up :)
The hazard flashers only worked occasionally.
The clock hasn't worked since 1973 (common problem, no big deal)
The auto-leveling rear suspension was replaced with a conventional setup before I bought it
I was lucky enough to buy this car out of storage with low miles, so I got to experience this car in essentially new condition.
The car had a few bad points, mainly the handling, and the gas mileage. That behemoth handled just like you'd expect it to - lots of lean when turning, dive when braking, and squat when accelerating (even after replacing the springs & shocks). It did not like corners. The steering was typical one-finger land yacht steering: no effort, no feel. The brakes were adequate, but you wouldn't want to push 'em too hard... the pedal was always mushy, with no feel, and the brakes would start to fade after one hard stop.
The fuel economy was absolutely horrible. My best, EVER, was a freakishly miraculous 18mpg on the highway (while light-footing it immediately after a thorough tune-up). Must've had a tail wind or something... More typical was 8mpg city, 14 highway; with the 27-gallon tank, I averaged about 250mi between fill-ups (usually filled up @ 1/8 of a tank). On a more nit-picky note, I thought the fake wood interior trim looked cheesy, and the radio definitely sounded as old as it was.
The ride quality of this car was pure old-style Cadillac. Total "leather armchair" comfort for six passengers (if you ignore seat belts, 8 will easily fit). This car had more rear legroom than I've ever seen... and it had fold-down foot rests! Wind noise was nonexistent below 80mph, barely there beyond that; you could only tell you were going that fast by looking at the speedometer. Plenty of times, I thought I was going 65, only to look down and see 90. To say that it rode smooth would be an understatement - this car smoothed out the nastiest, chunkiest, funkiest roads. If you're planning a road trip, I highly recommend getting one of these.
It also had a very high-quality feel to it (which I didn't expect from a '70s car). The doors, trunk, and hood shut as solidly as a bank vault. It never developed any squeaks or rattles, at least during the 13,000mi I owned it. Even the turn signal stalk felt nice - not like the "Am I gonna break this off?" plasticky feel of modern cars.
What this car liked to do most was go straight, and do it FAST. This is the ultimate highway car. I regularly, and easily, took it past 100mph. I once had it up to 115, and it was still pulling hard, but I had to back off 'cause the front end started vibrating (turns out the ball joints had been on their way out for some time). High speed wasn't it's only trick - this car had unbelievable acceleration, considering its size and weight. I had no problem keeping up with a '95 Mustang GT on the interstate during an impromptu "contest". Let me tell you, this thing was a sleeper. The combination of huge size (133" wheelbase, 234" long) and a huge engine helped me give many people a stoplight surprise. Nobody expects to get smoked by a car like this.
This was an excellent car; I'd still have it today if I could've afforded to keep fixing it. But, I was young & broke, and I didn't know how to work on cars back then, so all I could do was sell it when it accumulated too many problems. The car had been in storage since 1974, so going (almost overnight) from being stored to being a daily driver probably helped cause many of the parts failures, along with my "enthusiastic" driving habits.